Electrolytic detinning system.



H., GOLDSCHIVHDT.`

ELECTHOLYTIC DETINNING SYSTEM.

APPLICATION HLED FEB. 5. 1908.

l q l Al Patented Non 16, 1915.

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ELECTROLYTIC DETINNING SYSTEM.

APPLICATION FILED FEB. 5. 190s.

1,1 60,401 Patented Nov. 16, 1915.

2 SHEETS-SHEET ,32 L I 221 i 3l 6 .oliA/TANK acento/o HANS GOLDSCHMIDT, OF ESSEN-ON-THE-RUHR, GERMANY, ASSIGNOR TO GOLDSCHMIDT DETINNING COMPANY, OF NEW YORK, N. Y.,'A CORPORATION OF NEW JERSEY.

ELECTROLYTIC DE'IINNING SYSTEM.

i Specification of Letters Patent.` l

Patented Nov. 16, 1915.

Application 1aedY February 5, 1908. serial No. 414,440.

To f// IP/mm it' may concern.'

Be it known that I, HANS GoLnsCHMID'r, a subject of the King of Prussia, German Emperor. and resident of` Essen-onthe- Ruhr, Germany. have invented a certain new and useful Electrolytic Detinning System. of which the following is a specification. i

This invention relates to an electrolytic detinning system, and the lnain object of the invention is to provide an improved apparatus for detinning` tin scrap by means of an alkaline electrolyte.

In apparatus of this class as .constructed prior to my' invention, detinning was practised in single electrolytic cells only, as there was no way known of connecting up the cathode vessels of a group of electrolytic cells in such a manner as to obtain a free lowof the electrolyte through all the vessels of the group. It is well known that such a process is best conducted when the electrolyte is in motion, either constantly or intermittently. In an electrolytic process, however, in which the electrolyte is supplied to a plurality of vats, it is very difficult to maintain the circulation of the lye, and this difficulty is increased by reason of the fact that the connecting pipes are readily coated with tin through electro-deposition, and the normal free passageway for the flow of the electrolyte thereby obstructed. This stoppage of the pipes in the old method of detinning by means of an alkaline' electrolyte in .a single cathode vessel takes place quite rapidly, because'the tin deposited is not dense but is in a spongy condition occupy-V ing considerable space. Stoppage of the connecting pipes by this electrodeposited spongy tin is, as is well understood, due to electrolytic action, as the pipes themselves are conductors and are electrically connected by the electrolyte.

I have found as a result of experiments extending over a period of many years, that the circulation of the electrolyte through a series of electrolytic Vessels can be maintained and that the temperature of the electrolyte, which is always used in a heated condition, preferably at from 7 0o C. to 80D C., can also be kept up to the desired point without difficulty, thereby assuring a constant flow of electrolyte of good and substantially uniform composition without stoppage of the inlet and outlet pipes of the system. This result is accomplished chiefly by connecting up the "arious electrolytic vessels of the system in such a manner that the electrolyte will not flow in series there.

-ceives its individual supply directly from such source, the various vessels being conveniently connected by' branch inlet pipes, one for each vessel, to one or more main inlet pipes connected with a suitable source of supply or reservoir. In large plants the total number of electrolytic vessels may be divided into groups or rows, each constituting a unit, and provision madefor operating With one or more units, as required. All the vessels of a single series or unit should be arranged in substantially the same horizontal plane or slightly inclined, in order that the electrolyte may flow readily through the vessels from a common inlet to a common outlet pipe; although different ger of. stoppage of the flow of the electro-l lyte, it is preferable toymake use of inlet pipes which at the points of entrance to the electrolytic vessels are made of insulating material, as by this means all danger of electro-deposition ofthe tin on the walls of the inlet pipes is avoided.

An important featureof such a system is the determination of the proper sizes of the various pipes of the system through which the electrolyterflows, and the ratio of the pipes at different points in the circulating system to one another, particularly the ratio of the inlet pipes. All of these must be properly chosen and combined in order to obtain an uninterrupted circulation of the electrolyte through the system Without rewhich facilitate the circulation of the electrolyte through the various electrolytic vessels while the electrolyte is maintained at a suiiiciently high temperature and in a condition most favorable for even and thorough detinning, and various other features of the system-not before referred to, will be hereinafter described in connection with the accompanying drawings, in which:

Figure 1 is a plan illustrating diagra1nmatically an electrolytic detinning system embodying my invention; Fig. 2 is an end elevationof the same; Fig. 3 is a detail of parts of two electrolytic vessels illustrating the circuit connections thereof; Fig. 4 is a detail illustrating the supply reservoir and means for heating the electrolyte therein; Fig.v 5 is a similar view of the return reservoir for the electrolyte and means for heating the electrolyte therein; Fig. 6 is a detail illustrating one of the scrap-containing vessels or baskets supported in place in its cathode vessel. l

Similar characters designate like parts in all the figures of the drawings.

Referring first to Fig. 1, which illustrates one way in which the various elements of a system constructed in accordance with my present invention may be combined, 1 designates a source of supply from which an alkaline electrolyte may be delivered to the various electrolytic vessels of the system. This supply reservoir is preferably located above the other elements of the system, in-

order that the liquid may flow therefrom through the various pipes, vessels, etc. In

this case the high supply reservoir is'con-l nected by a pipe 2 to two main supply pipes 3 and 4, one of which supplies the'alkaline liquid to onev series of electrolytic vessels, while the other pipe 4 in a similar manner supplies the electrolyte to another series of vessels. Two branch supply pipes, such as 5 and 6, lead in this case from the main supply pipe 3 to the electrolytic vessels pr vats of the first series, these vessels being designated by 7, 8,9 and 10 respectively. At their ends the branch supply pipes are shown as forked, the -forks from the branch supply pipe 5 being designated by 11 and12, and those from the branch supply pipe 6 by 13 and 14. In a similar manner branch supply pipes 15 and 16 lead from the main supply pipe 4, and each in turn is forked, these .forks being designated by 17 and 18 for the branchpipe 15, and by 19 and 20 for the branch lpipey 16. The-vessels or vats of the second series or row are designated Especl tively by 21, 22, 23 and 24. The forked inlet pipes 11, 12, 13, 14, 17, 18, l19 and 20 are preferablyr provided withY suitable rcontrolling means, such as valves, for governing the flow of the electrolyte into the vessels of the second series. These controlling means or valves for the first series of vessels are designated by 25, and for the second series by 26.

It will be noticed that the pipes which supply the alkaline liquid to the different electrolytic vessels decrease in cross section from the supply reservoir 1 as they approach said vessels. This is a mattei' of great importance in order to control the iiow of the liquid properly and prevent excessive flow while at the same time assuring a sufficient flow of the liquid at the proper temperature `and in the proper condition. I have found in practice that a good ratio for the respective inlet pipes is to provide a main pipe from the main reservoir of from three to four inches in diameter, and to gradually decrease the areas of the intermediate pipes until the forked pipes are reached, which may have a diameter of about three-fourths of an inch. Moreover, it is desirable that the inlet ends of the forked inlet sections of the piping be located above the level of the liquid of the respective baths, the inlet sections themselves being in the preferred construction made of. non-conductingmateriah such as hard rubber; these bined in the system in this manner stoppage Lof inlet pipes due to electro-deposition of tin, is avoided, and in addition the proper flow of the liquid, which is always under considerable pressure because of the elevation of the supply reservoir, is assured. The supply reservoir will preferably be of large size for the purpose of keeping the electrolyte at the proper' temperature and in as uniform a condition as possible. In the construction shown the reservoir 1 (with a return reservoir which will be hereinafter specifically described) should be capable of holding from one-third to one-half of the Whole amount of alkaline liquid contained in the system. In practice I have used supply and return reservoirs the combined dimensions of which were from about ten tosuch as 29 andBO. It will be noticed that in every instance the electrolyte enters each Aelectrolytie vesselxnear one end thereof 'and at the upper side of the bath. In order that as complete a circulation of the liquid through the bath as possible may be obtained, itis preferable to place the outlet from each vessel at the opposite end thereof and substantially at the bottom of the vessel. This assures a thorough circulation of the alkaline electrolyte from the upper side of the bath at one end thereof to the bottom of the bath at the opposite end of the vessel, from which point it may be permitted to flowout through suitable outlet pipes which in practice may be arranged in a manner analogous to that before described with reference to the inlet pipes and are preferablyabout two inches in diameter. Thus, two main outlet pipes, such as 31 and 32, run in this case parallel with and below the two rows or series of electrolytic vessels 7 to 10 and 21 to 24, and are connected to the bottoms of the different vessels, there being a separate branch outlet from each vessel of the two series. This branch outlet from each electrolytic vessel is of different type from the branch connections at the inlet side of the system. These branch outlet pipes are constructed as communicating vertical tubes 33 and 34, open at their upper ends and connected at a point just below their upper ends by a short cross pipe 35. The pipe 33 connects with the lower vend of the electrolytic vessel, while the pipe 34 is connected directly to the main outlet pipe 31 or 32, as the case may be. Each one of the eight electrolytic vessels in the two series has a connection therefrom to its respective main outlet pipe of the character just described. The object of constructing the outlet from each electrolytic Vessel in this manner is to prevent the level of the bath rising above a predetermined point, the parts of the system being so constructed and combined that the electrolyte will overflow from the open upper ends of the pipes 33 and 34 whenever the conditions are such that the electrolyte rises too highv in the bath. l

The branch outlet pipes just described lead the slightly cooled electrolyte from the main outlet pipes 31and 32 to a return reservoir, such as 36, in which the liquid may be heated up before it is returned to the supply reservoir. The return reservoir is preferably constructed as shown in Fig. 5, from which it will be seen that it is a tank of large capacity heated by a suitable heater, such as the pipes 37, these pipes being supplied with steam in a manner similar to that before described with reference to the supply reservoir. The steam inlet and outlet pipes of the return reservoir are designated respectively by 38 and' 39.

The `ponnections between the various electrolyticvessels and the return reservoir 36 may be either open or closed conduits or electrolyte up into the supply reservoirv from the low return reservoir. This pump is preferably placed at a slightly lower level than the low return reservoir in order that the electrolyte may flow by gravity into the pump. The pump can then readily force it up into the high supply reservoir, this be ing the more readily accomplished when the electrolyte is brought into a more perfectly fluid condition by heating in the low reservoir in the manner just described. v l

In order to keep the electrolyte of the bathsv in as fluid a condition as possible (and. for the further purpose of electrically isolating the baths) it is desirable in practice to have each of the electrolytic vessels inclosed by a suitable non-conductor of heat and electricity. Both of these objects are accomplished by boxing the vessels, wooden boxes being preferably employed for the purpose, and an insulating airspace being left between the wooden box and the walls of the iron electrolytic vessels. These boxes are designated respectively by 42.

The electrolyticyesksels 7 to 10 and. 21 to 2.4 of the system are usually made of castiron, andconstitute the cathodes of the apparatus. rllhe anodes of the dierent electrolytic vessels may be of any suitable con struction, but l have found in practice that the most desirable for the purpose are scrapcontaining vessels or baskets, such as 43, made of sheet metal having openings therethrough of sulicient size to prevent the scrap from falling out, but as large as possible so as to reduce the resistance opposed to the passage of the current through each cell of the system.l These vessels or baskets, constituting with the scrap the anodes, are also of such a size as is most favorable to the economical use of the current in removing the tin from the scrap. The electrical connections in each cell may be any suitable for the purpose. Tn this case ll-have illustrated a plurality of parallel electrical connections from a supply conductor to each anode of a cell. The different cells of the two series are, however, in this construction connected in series with one another. O

F rom a suitable source of energy, such as the generator 44, current is fed to sectional. supply conductors, such as 45, there being one of these for each electrolytic cell. Preferably these sectional conductors are normally disconnected from one another, but are connected to the cathodes of adjoining cells. When the scrap-containing vessel or anode is in place in a cell the circuit is cornpleted from the sectional conductor 45 at one side of the cathode vessel to the opposite side thereof through the scrap and its container and the electrolyte, and current can low through the-two elements of such cell. ln each instance, however, the sectionalvsupply conductor 45 is insulated normally from the cathode, as is the bracket 4?.l

lt will be noticed that in the system shown "each cathode Vessel contains a plurality of anode baskets connected in parallel in the circuit'of each electrolytic cell. This permits the total quantity of tin scrap contained in any one cell of the system -to be divided up into a plurality of smaller portions.

`When it is necessary or desirable for any reason to cut out the electric current from any cell of the system, this may be accomplished by means of a suitable switch, such for example as that shown at 46. rlhis switch serves to connect one end of a secI tional supply conductor 45 .with an adjoining section of the supply conductor, thus short -circuiting the cell of that particular sectional supply conductor and directly connecting said sections of the supply conductor through the intermediate switch. Each of these sectionall conductors 45 is preferably a copper rod or bar insulated from the wall of the cathode` vessel. A strip of wood, such as 47, is usually employed as the insulating support for this conductor, said strip being fastened on the edge of the vessel. Each sectional conductor though insulated from its own cathode vessel is of course electrically connected with the other cathode vessel. l prefer to use an angular bond, such as 48, which is soldered or welded to the cathode and has its upper edge in line with that of the sectional' conductor of the cathode vessel to which it is fastened. Whenever two adjoining sectional supply conductors are con nected by their switch 46, the baskets in the short-circuited cell may be readily removed. Moreover, the controlling valve in the inlet pipe for that cell may be closed, the electro lyte drawn Off 'from the cathode vessel, and that vessel itself put out et action without interrupting the detinning process in the other cells of the series.

Normally the electric current flows without interruption through all the cells of the system. The current used, in order to accomplish the best results, that is, the most economical detinning, will preferably be one of very high amperage, say from eight hundred to one thousand amperes or more per square foot. The use of current oli' this high density is a matter oitmuch importance and was only determined uponafter exhaustive experimentswhich showed that it was the niemeer y most desirable under all the conditions present in a large commercial detinning plant.

rlhe composition of the electrolyte lor practical detinning on a commercial scale is also a matter of very great importance. l prefer to use a mixture of stannate of soda and caustic soda with an excess or" the caustic soda.` 'lhe alkaline electrolyte contains also carbonate ot soda, as the alkali takes up and unites with carbonio acid in the air. With an electrolyte of this composition the process carried on is a continuous one because of the regeneration of the liquid as it circulates through the system.

What l claim is;

1. ln a detinning system, the combination with a seriesof electrolytic vessels, and with means for passing an electric current through said vessels, of a main supply pipe, branch supply pipes leading from said main supply l pipe to each of said vessels and terminating in sections of insulating material at each vessel, and means for passing an electrolyte through said supply pipes and vessels.

2. ln a detinning system, the combination with a series of electrolytic vessels, and with means for passing an electric current through said vessels, of a main supply pipe.l branch supply pipes leading from said main supply pipe to each of said vessels and terminating in sections of insulating material at each vessel, and means for passing an electrolyte through said supply pipes and vessels from one end to the other of each vessel.

3. ln a detinning system, the combination with a series of electrolytic vessels, and with means for passing electric current of very high amperage through each of said vessels, of individual electric switches for short circuiting said vessels respectively, a high supply reservoir, connecting means between said supply lreservoir and said vessels for delivfering separate supplies of electrolyte to ditferent vessels oi' said series from said res ervoir, a low return reservoir, connecting means. between said Vessels and said return reservoir, and means for returning the elec trolyte from the return reservoir to the supply reservoir.

4. ln a detinning system, the combination with a series of electrolytic vessels, and with means for passing electric current of very high amperage through each of said vessels, of individual electric switches for short circuiting said vessels respectively, a high sup# ply reservoir, connecting means between said supply reservoir and said-Vessels for de livering separate supplies of electrolyte to dierent vessels of said seriesfrom said reservoir, a low return reservoir, connecting means between said vessels and said return reservoir, means for returning the electrolyte from the return reservoir to the supply iaeoaol f y w reservoir, and individual controlling means for governing the flow of the electrolyte at said vessels respectively.

5. In a detinning system, the combination with a series of electrolytic vessels, and with means for passing an electric cur-rent through said vessels, of a high supply reservoir, connecting means between said supply reservoir and said vessels for delivering ,i0 separate supplies of electrolyte to different vessels of said series from said reservoir, a low return reservoir, connecting means ben tween said vessels and said return reservoir, means for returning the electrolyte from the return reservoir to the supply reservoir,

and one or more slime-tanks in the connections between said vessels and the return reservoir.

6., In a system of the character described, in combination, a vat, a closed conduit circulating system for circulating an electrolyte therethrough, and enlargements in the conduits for collecting slime from the vat.

7. ln a system of the character described, in combination, a closed conduit circulating system for circulating an electrolyte therethrough, and enlargements in the return conduits of the system for collecting slime lfrom the vat.

8. In a system of the character described, in combination, a vat, a closed conduit circulating system for circulating an electrolyte therethrough, and slime tanks for collecting slime from the vat.

9. In a detinning system, a plurality of electrolytic vessels each having a cathode and a plurality of anodes electrically connected in parallel, electrical series connec tions between the anodes and cathodes of separate vessels, and means to supply the electrolyte to and withdraw it from each vessel separately.

10. ln a detinning system, a plurality of electrolytic vessels, electric connections beltween said vessels, means to short circuit any one of said vessels, means to supply the electrolyte to each of said vessels separately from a common source, and means to cut off the supply of the electrolyte to any one of said vessels. t

Signed at Newy York, in the county of New York, and State of New York, this 13th day of December, A. D. 1907.

HANS GLDSCHMDT.

l/Vitnesses;

CEAS. F. DANE, HUBERT E. ROGERS. 

